Alleged killer had been violent towards toddler's mother, court told

Two year old BJ Williams was allegedly murdered by his mother's partner.

The mother of a toddler allegedly murdered by her partner has told the Supreme Court she wished the man had taken his anger out on her, instead of her son.

Brock Michael Powell, 25, is standing trial accused of beating two-year-old BJ Williams to death at Melrose Park in Adelaide's south in January last year.

The court heard Powell claimed the boy had fallen out of bed and become wedged against a wardrobe.

But the prosecution said the toddler had blunt force trauma to his head and extensive bruising to his head, torso and genitals - consistent with a beating.

The child's mother, Latara Lee Hunt, yesterday gave evidence that she had argued with Powell before falling asleep in a separate part of the property, leaving BJ in the granny flat she shared with Powell.

Today, while being cross examined, defence lawyer Bill Boucaut asked Ms Hunt about a statement she gave to police after the incident.

"You told police you felt like the worst parent in the world for not being in the room," he said.

"That if you had been in the room, maybe it would have been you lying in hospital, not your son. What did you mean by that?"

Ms Hunt replied that "if I had been in the room, (Powell) would have taken his anger out on me, not my son, bluntly."

She also said Powell had become violent towards her about six months before the boy's death in an incident where he had thrown an ashtray at her and manhandled her.

Ms Hunt said that that was the only violent incident directed towards her by Powell during their relationship.